Surfscan SP1TBI Operations and Overview Course KLA-Tencor 660 Alder Drive Milpitas, CA 95035 The Surfscan SP1TBI is the newest in a series of Surfscan tools. It’s optics and capabilities are the next generation for the Surfscan 6000. Surfscan inspection systems are used for in-line detection of Yield Limiting Defects. Laser scattering technology and the registration of bright field information light provides sub-micron defect detection capability. The Surfscan family of instruments can be used to inspect the vast majority of unpatterned wafer materials (depending on the Surfscan model), for example, bare silicon, oxides, nitrides, epitaxial silicon, poly silicon, metals, and CMP. The Surfscan systems offer variable throughput measurement capability. Typical applications include qualification of wafer materials and deposition system performance, and contamination monitoring of wafers during yield limiting process steps such as metal and cmp. The types of surface defects detected include pits, particles, scratches, area defects, mounds, and dimples.

Surfscan 6XY0 The Surfscan SP1TBI is the newest in a series of Surfscan tools. It’s optics and capabilities are the next generation for the Surfscan 6000 family.

Unpatterned Surfscan Product Mix 6220 488nm, 30mW Ar laser 0.09µm sensitivity* smooth surfaces surface quality 6420 488nm, 30mW Ar laser 0.10µm sensitivity rough surfaces varying film thickness 6100 633n m, 5mW HeNe laser 0.15µm sensitivity smooth surfaces surface quality *All sensitivities refer to latex spheres on well-polished bare silicon

How does the Surfscan work? Illuminates wafer with scanning laser Uses normal incidence for 62X0 (SP1) Grazing-angle incidence for 64X0 (SP1TBI) Collects scattered light from particles Sizes and counts particles Accepts or rejects and then sorts wafers Displays information and writes information to file

Dark field and bright field basic definitions Dark field detection: refers to the collection and registration of scattered radiation. Bright field detection: refers to operations performed on the reflected light. The SP1 collects data from the dark field and bright field channels. The Surfscan 6200 collects data from only the dark field channel.

Inspection System Beam Dump Light Source Scattered Light Specular Beam Regardless of whether the system is a normal incidence system or an oblique incidence system, the goal is to collect light scattered from defects and to ignore the specular beam. The specular beam is the part of the incident beam that is reflected in a mirror like fashion (angle of incidence = angle of reflection). The specular beam contains no useful information for this type of defect detection technology. If it were collected it would destroy the signal to noise ratio required to detect particles. Incident Beam Substrate

Raster Scanning the Wafer Wafer Motion 85mm Raster Motion

LPDs & Haze Particles are High Amplitude & High Frequency Haze is Low Amplitude & Low Frequency

Dark Field (Normal)

Fundamentals of Light Scattering Light from laser illuminates particles on wafer and surrounding surface Particles and surface scatter light simultaneously Maximize detection of particle scatter and minimize detection of surface scatter

SP1TBI Optics & measurement principle Static Optics : Moving Sample The Surfscan SP1 includes Stationary Beam Technology (SBTTM) which provides a short beam path (of about 3 feet) with highly optimized illumination optics reducing the optical background to a few ppb and preserves the Gaussian beam profile. The Surfscan 6200 includes an oscillating scanning mirror and a much longer beam path (about 17 feet) which adds to the background noise of the system.

Scanning principles The wafer is transferred underneath the beam in a spiral motion The above allows for the following: -Edge exclusions < 1mm (from bevel) without sensitivity degradation -No edge artifacts since the PMT is not exposed to excessive light from the edges -Edge detection with below wafer sensor for wafer orientation and position -High throughput due to maximized time the laser spot is on the surface

Dark Field vs. Bright Field (Scattered Light vs. Reflected Light) Incident Light Scattered Light (Dark Field) Defect Scattered Light (Dark Field) Detector A (Dark Field) Reflected Light (Bright Field) The instrument contains a laser that operates at 30 mW power with a wavelength of 488nm. This laser illuminates the wafer surface producing scattered and reflected light. The intensity of the scattered light depends on the particle defect size encountered while the intensity of the reflected light depends on the surface defects. Detector B

Two Dark Field detection channels increase sensitivity and dynamic range The SP1 has two dark field detection channels: dark field wide collects scattered light from 25o to 70o and dark field narrow collects scattered light from 5o to 20o. The two channels allow for maximize data collection (avoid saturating the PMT), giving exceptional surface quality measurement with resolution better than 0.1ppb.

SP1 Dark-field optics optimized for detection uniformity fy µm-1 2.3 SP1 6220 1.0 -2.0 -1.0 1.0 2.0 fx µm-1 Some of the advantages of the Surfscan SP1 over the Surfscan 6220 can be realized by comparing the differences in the range of detection of the two tools. -1.0 -2.3

Surface scattering (haze) limits ability to detect particles on unpatterned wafers. Position in mm Photo- electrons from PMT photocathode Particle signal Threshold level Noise Background (100 photoelectrons)

Rotational collection symmetry is insensitive to defect orientation Amplitude Amplitude Signal response WITH rotational symmetry -Rotational collection symmetry ensures defect capture regardless of scattering direction, so that defect orientation and defect location are independent. -Scratches and other extended defects are easily detected time time Amplitude Amplitude Signal response WITHOUT rotational symmetry time

Light Scattering Inspection Process Detector Point Defect Collector Surface Information Dark Field / Bright Field Scan The SP1 translates and rotates the wafer under the illumination spot, thus ensuring that data is collected from all areas on the wafer surface. Because defects and irregularities on and in the wafer surface affect the scattering power of the surface, variations in the intensity of the scattered light can be correlated with surface features. The system processes the scattered-light data to produce data, called scan data, that identifies the size and location of surface features. Defect Display Surface Data Display

LPDs & Areas scatter light into different polar angles narrow collector wide collector small PSL sphere Scattering Intensity large PSL sphere Point defects LPDs: Surface defects that are significantly smaller than the laser spot size and can include pits or particles (ppm or um LSE). Areas: Surface defects that scatter light at an intensity that exceeds the saturation threshold of the collection optics (um LSE). Haze: Light scattered from defects that are distributed over areas larger than the laser spot size (ppm). Si Surface 20 40 60 80 Scattering Polar Angle [degree]

Different defect types scatter light into different polar angles ... … allowing distinction of defect types (particle) (crystal defect)

Distinction of Defects with multiple DF-Collectors

Dark Field (Oblique)

TBI Optics Layout Dark Field Wide PMT Narrow PMT Ellipsoidal Collector Oblique Incidence Beam Normal Wafer Lens Beam Position CCD Deflection Wedge ND, polarizers Apertures

Scattering Cross-Section LSE diameter and geometric diameter are not the same. All of these particles have LSE diameters of 100 nm on a Surfscan 6200. Si 3.88 72 nm Cu 1.14-2.52i 72 nm Al 0.75-5.75i 75 nm Si3N4 2.04 90 nm PSL 1.60* 100 nm SiO2 1.47 105 nm Index LSE *bulk refractive index at 488 nm All of these spheres have an LSE diameter of 100 nm on a Surfscan 6200. However, only the PSL sphere has a geometric diameter of 100 nm. The biggest contributor to the change in diameter is the refractive index. For this picture, I have listed the bulk refractive index of the material. For dielectrics, you can see that the higher the index, the smaller the geometric diameter. Or in other words, the higher the index, the stronger a sphere of a particular size scatters. The metals, Cu and Al, have a little different story. For these materials I have listed the complex refractive index, and you can see that the metals have a strong imaginary component. This absorptive contribution to light scattering dominates in the calculation of scattering cross-section. You’ll notice that almost all of the materials scatter stronger than latex with the notable exception of oxide. This means that when we specify the Surfscan as having a minimum detectable particle size of 100 nm, it can really see a 72 nm particle of silicon. LSE : Laboratory scale enclosure

PSL Full deposition Spot deposition PSL Wafer Standards are used to calibrate the size response curves of Scanning Surface Inspection Systems (SSIS) manufactured by KLA-Tencor, Topcon, ADE and Hitachi.  PSL Wafer Standards are also used to evaluate how well the SSIS performs a uniform surface scan across the wafer.

최근 관련 기사 KLA-Tencor사는 자사의 결함검출 툴인 Surfscan SP1 제품군에 결함의 검출, 분석과 공정 감시 기능을 추가했다. Monitor eXpert(MX 4.0)라는 명칭의 소프트웨어 옵션 모음은 이 툴이 추가적인 비용을 들이지 않고도 단일 주사로 공정 감시 정보와 벤치마크 결함 검출 기능을 제공할 수 있게 한다. 웨이퍼와 IC 제조자는 Surfscan SP1에 MX 4.0을 사용하면 표면 거칠기, 낮은 k 유전체의 유공률 수준, 방식제와 박막 두께의 균일화, 화학 기계 연마(CMP) 패드의 상태조절과 연마 균일성, 구리의 전자화학식 증착(ECD)을 하는 동안 용액의 화학적 성분 변경을 비롯하여 동시에 다양한 경과 특성에 대한 결함을 검출하고 필수적인 통찰력을 확보할 수 있다. MX 4.0의 웨이퍼 탁도 감시 기능은 정상 조작 창의 바깥으로 벗어나기 시작하는 공정에 대해 조기에 검출 경보를 제공한다. 이 소프트웨어의 업그레이드 판에는 검사를 하는 동안 비정상적인 탁도 패턴을 찾아내고 사용자가 공정 기술자를 위해 이것들을 이전에는 탐색 및 관측이 불가능하던 결함으로 판별할 수 있게 하는 새로운 탁도 분석 기능도 포함되어 있다.